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Studies on Non-Newtonian Behavior in Slit-flow rheometer at Unsteady flow
Halama, Lukáš ; Vimmr, Jan (referee) ; Roupec, Jakub (advisor)
The thesis deals with the description of the unstable flow of non-Newtonian fluid in a slit-flow rheometer, which negatively affects its behaviour. The initiators of unstable fluid flow are the roughness of the rheometer slit walls, the slip on the rheometer walls, and the influence of the inlet and outlet region geometry of the rheometer slit. The work contains methodical procedures for mathematical consideration of individual unstable fluid flow initiators and design of change of slit geometry of slit-flow rheometer. Part of the work is also a comparison of the most commonly used rheological models, derivation of general relations for the creation of the velocity profile of individual rheological models and their subsequent implementation in the rheological application, which significantly simplifies the process of evaluation of measured data when measured on slit-flow rheometer. This application can be used to determine basic parameters in CFD simulations or as a teaching aid.
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Modification of the Algebraic Transition Model for Wall Roughness Effect Including a Rough Strip
Straka, P. ; Příhoda, Jaromír
The contribution deals with the simulation of the laminar/turbulent transition on a rough wall. The algebraic transition model taking into account wall roughness according to Straka and Příhoda [8] was further extended for the effect of short rough strip near the leading edge. The proposed correlation was tested by means of incompressible flow over a flat plate covered by sand paper and around the NACA 0012 airfoil with a rough strip near the leading edge. The agreement with experiments is appropriate nevertheless the applicability of the correlation is limited due to the lack of relevant experimental results.
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Studies on Non-Newtonian Behavior in Slit-flow rheometer at Unsteady flow
Halama, Lukáš ; Vimmr, Jan (referee) ; Roupec, Jakub (advisor)
The thesis deals with the description of the unstable flow of non-Newtonian fluid in a slit-flow rheometer, which negatively affects its behaviour. The initiators of unstable fluid flow are the roughness of the rheometer slit walls, the slip on the rheometer walls, and the influence of the inlet and outlet region geometry of the rheometer slit. The work contains methodical procedures for mathematical consideration of individual unstable fluid flow initiators and design of change of slit geometry of slit-flow rheometer. Part of the work is also a comparison of the most commonly used rheological models, derivation of general relations for the creation of the velocity profile of individual rheological models and their subsequent implementation in the rheological application, which significantly simplifies the process of evaluation of measured data when measured on slit-flow rheometer. This application can be used to determine basic parameters in CFD simulations or as a teaching aid.
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Modelling of compressible flow through turbine blade cascade with various wall roughness
Příhoda, Jaromír ; Straka, P.
The contribution deals with the numerical simulation of 2D compressible flow through a turbine cascade with smooth and rough blades using the EARSM turbulence model of Hellsten. Predictions were carried out at the Reynolds number Re2is = 850000 for various Mach numbers. The algebraic bypass transition model was applied for comparison in case of smooth blades. Predicted values of the loss coefficient and the flow outlet angle were compared with experimental data for the turbine cascade VS33 with smooth and rough blades of wall roughness.
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Numerical Simulation of Turbulent Flows Through Turbine Cascade With Rough Blades
Fürst, J. ; Louda, Petr ; Příhoda, Jaromír
The article deals with numerical simulation of turbulent compressible flows through 2D model of a turbine with rough blades. The mathematical model is based on the Favre-averaged Navier-Stokes equations combined with several two-equations turbulence models. The wall roughness is modeled using an appropriate boundary condition for specific dissipation rate. The comparison with experimental data shows correct increase of energy losses in the case of increased wall roughness.
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